Nociceptive Mechanisms Underlying Sickle Cell Pain

Medical College Of Wisconsin, Milwaukee WI

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Abstract

DESCRIPTION (provided by applicant): The overall goal of this project is to determine the contribution of sensory neuron mitochondrial dysfunction and TRP channel sensitization to pain in sickle cell disease (SCD), including the development of chronic pain. SCD is accompanied by crippling pain during acute sickling episodes that increases in severity and frequency with age. By adulthood, approximately 50% of SCD patients also suffer from chronic pain. SCD involves repeated ischemia-reperfusion injury and increased neutrophil numbers/activity, which results in elevated reactive oxygen species (ROS) generation and oxidative stress. This can lead to mitochondrial dysfunction and sensitization of Transient Receptor Potential (TRP) ion channels. We show that mice with severe SCD exhibit evidence for ongoing pain and pronounced pain-like behavior in response to cold, mechanical and heat stimuli. Our preliminary data also indicate that sensory neurons from sickle mice have severely dysfunctional mitochondria. We hypothesize that ROS and oxidative stress induce mitochondrial dysfunction and TRP channel sensitization in sickle sensory neurons, leading to the chronic pain and thermal hypersensitivity that is characteristic of this devastating disease. Aim 1 will determine the time course of neuronal mitochondrial dysfunction and pain sensitivity in sickle mice from age 2 to 12 weeks. Aim 2 will determine whether sensitized TRPA1 or TRPM8 channels underlie the cold hypersensitivity and primary afferent sensitization in sickle mice. Aim 3 will determine whether treatment with mitochondrial-targeted antioxidants reverses the pain behavior and primary afferent sensitization in sickle mice. These interrelated Aims provide a multifaceted approach that will define the mechanisms by which mitochondrial dysfunction and TRP channel sensitization lead to the devastating pain observed in SCD. Furthermore, this study targets specific cold-sensitive ion channels (TRPA1 and TRPM8) on sensory neurons because cold pain and cold hypersensitivity are a major complaint of patients with SCD. Data from this study will improve our understanding of the complex SCD pain syndromes and should aid in identifying novel therapeutic targets